I’ve changed the for sale system to use normal WordPress posts with the For Sale category selected.
To see the category selector when writing a post, click the black cog at the top right and select the post tab. halfway down the screen you’ll see the categories section, expand that and tick ‘For Sale’
Add images by pressing /image on a new line and upload your images using the dialog which appears, keep them to a small size.
When you’re finished, press the blue ‘Publish’ button to post your item to the site